1. Field of the Invention
The present invention relates to a differential amplifier, and more particularly, to a capacitive feedback fully-differential amplifier.
2. Discussion of the Related Art
Currently, amplifiers are being used in various electronic circuits, and such amplifiers may be used in various electronic devices. One type of amplifier used in such various electronic devices is a differential amplifier, which incorporates a resistive feedback structure and a capacitive feedback structure. Problems involved in differential amplifiers having a resistive feedback structure, include that a direct current (DC) offset is amplified in the output.
In contrast, the capacitive feedback structure has an advantage over the resistive feedback structure in that the capacitive feedback structure transmits and amplifies an alternating current (AC) signal while blocking direct current (DC) components. However, when capacitors are connected to the differential amplifier having a capacitive feedback structure, floating nodes may be generated since amplifying terminals are formed. In a floating node, since its potential is not fixed and varies based on the surrounding environment, output of the differential amplifier varies due to the non-fixed (variable) floating node.
In the related art, in order to fix the voltage of the floating node, a resistor having very high resistance may be connected to an output terminal for feedback. In particular, since the resistor having very high resistance does not affect the output of the amplifying terminal when the resistance is at least about 1 giga-ohm, a substantial area is required to acquire such a high resistance, thereby making implementation of such an amplifier difficult using a sub-micron complementary metal oxide semiconductor (CMOS) process.
The above information disclosed in this background section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.